General differential equation solution for Kepler Problem

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Discussion Overview

The discussion revolves around the Kepler problem and the possibility of finding a general solution for the motion of two or more bodies under gravitational influence. Participants explore the feasibility of deriving a formula that incorporates initial conditions such as masses, positions, and velocities, and whether such a solution can be generalized to n-body systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions if there is a specific form of the solution to the Kepler problem that allows for direct input of masses, velocities, and positions to obtain equations of motion.
  • Another participant suggests that while it is theoretically possible to create such a formula, it would be impractically long, and step-by-step calculations are preferred.
  • Concerns are raised about the complexity of trajectories in systems with three or more bodies, noting that small differences in initial conditions can lead to chaotic behavior.
  • A participant mentions that there is no general solution for three or more bodies, but numerical methods can be used to approximate solutions.
  • One participant expresses uncertainty about their knowledge of physics, while another counters that they possess more understanding than typical high school students.

Areas of Agreement / Disagreement

Participants generally agree that there is no general analytical solution for three or more bodies in the context of the Kepler problem, and that numerical methods are necessary for approximating solutions. However, there is no consensus on the practicality of deriving a usable formula for two bodies.

Contextual Notes

Participants acknowledge limitations in their understanding of physics and the complexities involved in solving the n-body problem, particularly regarding chaotic dynamics and the impracticality of long formulas.

Steve Jones
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To be honest, I don't know any physics. I am a high school student who has taken high school physics, but America's education system isn't known for teaching much more than Newton's laws. I have, however, taken Multivariable/Vector calculus, so I have a decent math background.

I was wondering is there is a specific form of the solution to the Kepler problem. The initial conditions would be the masses, positions, and velocities. I have found this link to the wikipedia solution, but I wonder if it is possible to have a solution that I can just plug the masses, velocities, and positions in and get an equation for the motion of both bodies.

Also, I wonder if that solution could be generalized to include however many bodies you want. The wikipedia article said it could not be solve in terms of first integrals, but I wonder if there is a general solution for n-bodies.

Please be nice to me :P I don't possesses a vast knowledge of physics (or any at all). I also don't know if this thread is in the right place either.
 
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Steve Jones said:
I have found this link to the wikipedia solution, but I wonder if it is possible to have a solution that I can just plug the masses, velocities, and positions in and get an equation for the motion of both bodies.
It is possible to make that, but the formula would be too long to be practical. It is easier to calculate all the relevant quantities step by step, as shown in the article and books.
Steve Jones said:
Also, I wonder if that solution could be generalized to include however many bodies you want. The wikipedia article said it could not be solve in terms of first integrals, but I wonder if there is a general solution for n-bodies.
There is not.
 
Thank you for the response.
 
The problem is that from three bodies on, in general, the trajectories get very erratic. Minute differences between starting points make the difference between a stable situation and one where one of the bodies gets ejected from the system.
 
Steve Jones said:
To be honest, I don't know any physics. I am a high school student who has taken high school physics, but America's education system isn't known for teaching much more than Newton's laws. I have, however, taken Multivariable/Vector calculus, so I have a decent math background.
snipAlso, I wonder if that solution could be generalized to include however many bodies you want. The wikipedia article said it could not be solve in terms of first integrals, but I wonder if there is a general solution for n-bodies.

Please be nice to me :P I don't possesses a vast knowledge of physics (or any at all). I also don't know if this thread is in the right place either.

Hi Steve: You know a heck of a lot more than most high schoolers. Most of them wouldn't know a differential equation from differential fluid.
In classical mechanics courses following general college physics they discuss the "three-body problem". There is no general solution to 3 or more bodies. You can, however, use numerical methods to approximate a solution to whatever degree you want.
I disagree with your statement that you don't know any physics.
 

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